This is an insectivorous plant with small .5mm traps. The traps which are triggered by small nematodes or any other animals that are of the right size are sucked into the awaiting bladder by the rapid expansion of this cavity when small hairs are triggered. Utricularia lives in water and requires the correct ph and purity. The dark brown area is trapped prey. Enzymes from the plant are secreted that allow for absorption and digestion. This plant was seen in a small spring used for drinking water. This was a delightful find by Dr. Eisenberg. I have studied insectivorous plants for 25 years and the Utricularia is a very delicate and fascinating plant.